1. Field
This invention relates generally to ejectable projectiles and propellants for ejecting those projectiles from casings within which they are disposed. Specifically, this invention is directed to solid propellant systems for generating gases which eject projectiles from canisters or casings at a controlled velocity.
2. State of the Art
Projectiles, such as rockets, missiles, and the like, are well-known in the aerospace and military industries. Propellants which are associated with such projectiles are also well-known. Some projectiles, such as rockets or missiles, typically comprise a warhead and an internal motor for urging the projectile forward to its target. Internal motors for driving the projectile may be of a solid propellant type, a liquid propellant type, or some other type known to those skilled in the art. Frequently, rockets, missiles, and similar projectiles are disposed within a closed-end casing or canister prior to firing. When fired, projectiles of this type must first be ejected from the canister. Projectiles which have an internal motor, i.e. rockets, must first be ejected from the canister before the rocket motor is ignited to prevent damage to the canister. Projectiles which do not have internal motors, i.e. bomblets, submunitions, flares, etc., must also be ejected from the canister for glide or free fall to a chosen target.
Solid propellant grains generally take many forms. For example, some propellants are poured into the rocket casing to fill a substantial percentage of it. Other propellant grains take the form of a carpet roll which is placed in the rocket casing end-to-end. Examples of such propellants are disclosed in U.S. Pat. No. 3,763,787 to Schultz, issued Oct. 9, 1973, and U.S. Pat. No. 3,737,348 to Schultz, issued Jun. 5, 1973, both of which disclose a double base propellant applied to both sides of a reinforcing material and rolled into a carpet-type roll. The reinforcing material provides a space between the propellant surfaces sufficient to provide a very large area of combustion. The roll is placed within a rocket motor casing so that the roll is in a cross-sectional orientation to the casing. The carpet roll is bonded to the inner casing of the rocket motor and is attached by adhesive means to a head plate.
U.S. Pat. No. 4,792,423 to Craig, et al., issued Dec. 20, 1988, discloses the molding together of binder, fuel, oxidizer, and additives to form a propellant which may then be formed into any desired shape, including filament winding, helical roll, and carpet roll. Craig is particularly directed to molding of propellant components to achieve variable burn rates and suggests that a particular shape may help achieve a variable burn.
These and other prior art propellant grain configurations are typically designed to provide a geometrically increasing surface area of propellant for burning. That is, as the exposed surface of the propellant burns, it exposes an ever increasing surface area for burning, and the resulting generation of gas from the burning propellant increases geometrically.
Consequently, there remains a need for a propellant gas-generating system for use with ejectable projectiles which provides controlled burning of the propellant at a rate related to the displacement of the projectile. There is also a need for a propellant system which provides controlled burning as a function of the acceleration of the projectile.